The role of a metal ion within Nafion upon its physical and gas transport properties

The physical and transport properties of Li+, Na+, K+, and Ca2+ neutralized Nafion were compared to its acid form. Nafion crystallinity was disrupted with a variety of cations while average d-spacing remained constant. Higher thermal stability in metal ion exchanged Nafion was observed using TGA. Ionic interactions were probed by DMA and spectroscopic techniques. Divalent Ca2+ exhibited a distinctive influence on the chain’s mobility as compared to monovalent ions. The interaction strength cation exchanged Nafion decreased in the following order: Li+ > Ca2+ > Na+ > K+. Gas permeability increases were primarily attributed to gas solubility. Nafion had a higher gas activation energy Ep, but its permeability was lower than unsulfonated PTFE.